﻿#include<stdio.h>
int Jump(int n)
{
	if (n < 3)
	{
		return n;
	}
	else
	{
		return Jump(n - 1) + Jump(n - 2);
	}
}
int  main()
{
	int n = 0;
	scanf_s("%d", &n);
	int ret = Jump(n);
	printf("%d", ret);
	return 0;
}